This paper proposes an argumentation language to support and archive argumentation in teamwork. Teamwork effectiveness can be improved by continuous, exchange of information, arguments and by joint agreements on actions. The proposed language is intended to be used as a mechanism for negotiation support and organizational repository, For each task of the development process, a decision problem can be seen as one which requires the team members to identify what action to take and what resources are affected by each action. The language is next applied to support argumentation in software development.